Studying Quakes: A Shaky Proposition

December 04, 1991|By Merrill Goozner, Chicago Tribune.

TOKYO — This bustling metropolis is on the move.

Over at the Japan Meteorological Agency, a stone`s throw from the Imperial Palace, deputy director Masayuki Kuwashima and his team of 97 seismologists keep track of how often and how much and try to predict, mostly unsuccessfully, when.

Last year, according to Kuwashima, the earth beneath Tokyo moved 4,648 times. Nearly 50 of those quakes were strong enough to be felt by humans.

This year is shaping up as another banner year. Last month`s ``quite big`` earthquake-4.9 on the Richter scale-was strong enough to halt rail and air traffic for half an hour. Fortunately, because it was centered 50 miles below Tokyo Bay, there was no tidal wave-the dreaded tsunami.

``From a geophysical standpoint, Tokyo is a big mistake,`` said Kuwashima, whose section is overoptimistically called the Earthquake Prediction Information Division.

It`s unfortunate, Kuwashima laments, that the leaders of the Meiji restoration decided in the 19th Century to move Japan`s capital city from seismically mundane Kyoto to rockin` and rollin` Edo, soon renamed Tokyo. Today, a metropolitan area of 28 million people rests atop incredibly expensive land only a morbidly curious geophysicist should love.

The city already has paid once for that move. In 1923 a quake measuring 7.9 killed more than 140,000 residents of what was then a much smaller city. The subsequent fires leveled more than a half-million buildings.

The scientific explanation for Tokyo`s excessive shimmers is simple enough. Most of the world`s earthquake zones are located above a fault line that marks where two plates of the Earth`s crust come together.

Tokyo is above three plates-the Eurasian, the Pacific and the Philippine- making it one of the most active quake zones on Earth with about 10 percent of all reported activity. The constant jostling frays the nerves of locals and keeps government and academic prognosticators guessing when the next big jishin will hit.

``The friction between the Philippine plate and the Pacific plate should result in an earthquake every 200 years,`` said Kuwashima, suggesting the current generation may not experience an earthquake as severe as the 1923 temblor.

Kuwashima dismisses the widespread belief that a big earthquake is overdue. ``Some people believe the cycle is only 60 or 70 years, but they`re using statistical models, not geophysics,`` he said.

Other experts disagree.

``What we are concerned about most is `chokka-gata,` an earthquake directly under Tokyo and near the surface,`` said Katsumasa Abe, a professor at the University of Tokyo`s Earthquake Research Institute. ``This could happen at any time.``

In a city where sidewalk fortunetellers earn a good living and astrologists` yearend predictions include the months of anticipated major quakes as well as political shakeups and emerging social trends, the search for the perfect earthquake prognosticator is never-ending.

At Tokyo Metropolitan Fishery, an experimental station run by the city, scientists have been monitoring the movements of catfish since 1978. Deputy director Shinichiro Egawa insists the predictor has nothing to do with the pre-Meiji belief that earthquakes were caused by a giant catfish living underground.

``Catfish usually do not move a lot,`` Egawa said, ``but our records show that if they move a lot for two hours, an earthquake soon follows.``

Unfortunately, his catfish can predict earthquakes anywhere from 20 minutes to 10 days ahead of time, the equivalent of predicting below-freezing weather in Chicago for December.

Earthquake preparation, however, is a serious business. Every Sept. 1, the anniversary of the 1923 catastrophe, local ward offices sponsor preparedness drills. Construction, especially in the high-rise districts, is tightly regulated, although Shinjuku ward, home of the city`s tallest buildings, was largely spared in 1923.

Still, a government panel last year predicted that another 7.9 quake would result in nearly 10,000 deaths, 150,000 injuries and burn 26 percent of Tokyo to the ground.

The job of the earthquake prediction center is to provide some warning before such a catastrophe hits. Inside a drab green government office, the silent hum of computers, the back-and-forth etching of seismographs and the giant wall map of Japan suggest a war room. Data pour in from 54 monitoring stations around the country and at sea, as well as from earthquake monitoring stations throughout the Pacific and on the west coasts of the U.S. and South America. (The 8.2 earthquake in Chile in 1960 caused a 15-foot tsunami in Japan 19 hours later that killed 142 people.)

Under a glass panel in the center of the room sit 19 red buttons, connected to the police, radio stations and government offices in the major coastal areas of Japan`s four major islands. The hope is that by quickly pinpointing and evaluating earthquakes at sea, the center can give advance warning of tsunamis, giant waves that move at speeds up to 125 m.p.h.

``It`s impossible to predict any earthquake,`` Kuwashima said. ``But by analyzing earthquakes at sea very quickly, we can provide advance warning of tsunamis.``

But even that is an imprecise science. On Sept. 3, the center sent out a tsunami warning.